


big brother is finally big

by spamanootnoot



Category: Undertale (Video Game)
Genre: Alternate Universe, Bara Sans, Dom Sans, Dubious Consent, Ecto-Genitalia (Undertale), Incest, M/M, Mating Cycles/In Heat, Overstimulation, Plot What Plot/Porn Without Plot, Sibling Incest, Size Difference, Sub Papyrus, Underfell Papyrus, Underfell Sans
Language: English
Status: Completed
Published: 2017-10-18
Updated: 2017-10-18
Packaged: 2019-01-19 04:18:52
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 1,279
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/12402861
Author URL: https://archiveofourown.org/users/spamanootnoot/pseuds/spamanootnoot
Summary: Sans wreck the heck outta' Papyrus.





	big brother is finally big

Half-opened eyes reads through the mind-numbingly boring reports from the canine unit, and you skipped most of them to see the most important parts of them all. 

Two monsters were dusted and one were found nearly dead. 

You sighed and rests your forehead on your palm. At least they had enough time to aided the monster before its too late. Trying to keep the Snowdin's residents safe from outside danger while hiding the fact from the king to not face his wrath was tiring. You really need to investigate these cases of random dusting around the Snowdin area because you know for sure that while it rough around the edges here, most of them tolerate each other and the most they would do is either fight in the bar or hold each other back from causing a scene. 

You knew they were scared of you and you took advantage of that. But all of this works resulted in you not getting any sleep and completely forgetting about eating at all. Ugh.

You need to get some more coffee.

Rising up from your seat, you went out of your room and took small and tired steps, planning to head downstairs and go to the kitchen. But all of a sudden, halfway through the hallway, you stopped at your brother's room when you smelled an odd but familiar smell. Sans is in heat.

Sans.

Shit, did you literally forgot that your brother existed too. Screw coffee, you've been ignoring him at the time when you're most needed and that is unacceptable.

Without a single thought, you twisted the knob and immediately opened the door, surprises that its not locked. When you stepped inside his room, the strong smell of his heat was intoxicating you, making you a bit nausea from the smell. Closing the door behind you, you searched around the small room for your brother but he was nowhere to be found. Odd. His room sure is reek with his smell but he isn't around. You walked towards his bed and looked at the mattress, there, you noticed red stains fading into the sheets.

He's definitely somewhere. But where is-?!

"lookin' for me?"

Startled, you turned your head and widened at the sight. There, was your brother, who has grown quite in a large scale. He, who used to be 4'9 is now even bigger and taller than you, assuming he's 8 feet tall. Your eyes examined him from head to toe, failing to ignore the big bulge coming from his shorts which made you looked back directly at his face in embarrassment.

"like what yer' seeing, sweetheart?"

He looks at you, smirk widening and pupils filled with lust. Before you had the chance to talk, he pushed you down onto his bed as your back leaned roughly onto the wall and trapping you between his large build. Yelping in surprise when he quickly dives into your neck, helpless as his teeth pressed roughly into the every spots of your right collarbone. Gasping from the overwhelmingly harsh treatment on your clavicle, sparks of pleasures went down into your pelvis. Your voice pitched up even more when you felt his hand slipping into your sweater and beneath your ribcage as he softly grips your soul, fondling it a little bit before pulling it out of your ribcage.

He leans back from your abused neck and slid his tongue out from his mouth, slightly drooling from the sight of your upside-down grey soul with a tint of transparent red magic glowing on the outside of the soul. It was not long before he slowly pushed his tongue against your soul, gliding it to the every inches of your fragile soul. This resulted in you writhing below him, hands over your teeth which only makes out muffled noises of you gasping and moaning with everytime he grazed that tongue of his on your soul.

Your body arched in surprise as he pressed his tongue at the center of yourself, which made your body momentarily jolted in pleasure multiple as he kept on rubbing his tongue on that particular spot.

"sensitive here, eh?"

"Wai-ihh- Sa-aahns! S-stop, I'm gon-gonna- hhnnggaaa!!"

Spurts of your magic went flying over to your brother's face. Panting to no end, your body laid limp on the sheets. Despite from the exhaustion, your magic didn't fail to pooled around your pelvis and forming an already-dripping cunt. 

Your brother seemed to be quite delighted by the sight as he licks off the remaining magic of yours on his face and towers over you, letting your soul to floats back into your ribcage, then his hand went over his pants and pulled down his zipper to free his hardened cock. The sight took you by surprise as before you was your brother's absolutely thick and long cock, not the ones that you usually see which is way less extreme than what is displayed in front of you.

As he positioned his cock right before your entrance, spreading your legs and then rubbing the tip of it on the wet folds in a teasing manner in which made your pussy to pulsed in desperation. But as soon as he started to slowly made his way in, your teeth began grinding against together and when the tip was in and the thick shaft started to made its way into you in a slightly faster pace than before, you started to writhed beneath him, spine jerking upwards in utmost pain and pleasure as your hand dug into the mattress.

"Take i-it ou-hhnn.. Sans, p-please! Its too - ahhhn - b-big."

"shhh, sweetcakes, I'm gonna take /good/ care of you."

A pained scream escaped your mouth when he thrusted into you by surprise, you could feel yourself clenching tightly around his cock, your cum coating his cock almost immediately as you let out a rippled moan from your sudden stimulation.

"w-woah. just like that? such a slut you are, aren't cha'?"

At this moment, you were biting down your sweaters as muffled moans and screams could only be heard from your mouth as tears streamed down your face from the overwhelming sense of pain and pleasure. This only made his grin grew wider as his skull leans closer to your neck, you could feel him breathing heavily beneath you as he holds both of your knees only spreading it much more wider making you gasps. You were sure that you heard some cracking noises below by just him doing that.

Then, he pushed his hips into you once again. Again and again. Rocking into you in a fast and desperate speed as the bed beneath you two rattled against the unsteady rhythm. The cloth between your teeth was no longer there after he had taken the sudden action, leaving you whimpering and screaming upon how violent his thrusting was.

"S-Sans, st-ss-stop! Sl-slo-slower!!" You cried beneath him, clutching onto the mattress with a tight grip.

"Please!" You frantically chanted in desperation only to be ignored by the latter.

"oh- go-god, you feel so g-good, sweetheart.."

Throwing your head back, your trembling hands scratched onto the cloth of it the sheets as you felt yourself coming again but his thrusting didn't stop even when you're clenching around him in which made you cried out from the unbearable pleasure and pain.

"s-so tight around me, hnngh, goo-good boy.. ahh-hhnn, sweetie, i-i'm gonna c-aAAHNGH-!"

When his seeds filled you up, you were close to passing out as the sight of your brother blurred out and eventually went dark, the only thing you heard and felt before you were completely knocked out was the clanking of your brother's teeth against your forehead.

"goodnight, dear."


End file.
